Prepare the Roux : Begin by melting the unsalted butter in a medium saucepan over medium heat. Once fully melted, incorporate the all-purpose flour and stir continuously for approximately one minute. This process eliminates the raw flour flavor and forms a rich, thick base for the mac and cheese.

Incorporate the Liquids : Gradually add the milk and half-and-half to the roux while whisking constantly. Once fully combined, mix in the ground mustard, salt, and pepper. Continue whisking to prevent lumps from forming, allowing the mixture to simmer for a few minutes until it begins to thicken.

Melt the Cheese : Remove the saucepan from the heat and incrementally add the shredded cheddar cheese, stirring continuously to ensure a smooth blend. The cheese should fully melt into the sauce, creating a rich, cheesy mixture.

Combine with Pasta : After draining and rinsing the cooked elbow macaroni, return it to your baking dish. Pour the creamy cheese sauce over the macaroni, ensuring each piece is thoroughly coated. Stir well to achieve an even distribution of the cheese sauce throughout the pasta.

Prepare the Topping : In a small bowl, combine the Panko bread crumbs with the melted butter. This mixture creates a crunchy topping that will enhance the texture of the dish. Evenly sprinkle it over the macaroni and cheese.

Bake the Dish : Cover the baking dish with aluminum foil and place it in a preheated oven set to 350°F (175°C). Bake for 40 to 45 minutes. After this time, remove the foil and switch the oven to broil for an additional minute or two, watching closely to prevent burning, until the topping is golden brown and crispy.

Rest Before Serving : Once out of the oven, allow the Baked Mac and Cheese to rest for about 5 minutes to set. After this resting period, serve and enjoy this creamy, cheesy delight with its perfectly crunchy topping—truly the essence of comfort food!